Twenty-three-year-old Saskia Reeves-Priestley was at work when she suddenly collapsed.
"I just felt really dizzy, really nauseous, was having heart palpitations and was really hot," she says.
Saskia, a special educational needs teacher, was a keen goalkeeper who played football four times a week and felt fit and healthy. While her symptoms are not directly linked to vitamin D deficiency - she realised something was wrong.
In the UK, low vitamin D rates are increasing in some age groups - particularly in girls and young women.
